b_panther_* said:
“It doesn't go through the gain stages that a microphone signal needs.”
I don’t know much about pro recording or microphone gain stages. Could you explain how they are different from amplifying a line level signal?
The lower a signal is, the more stages of gain it needs to go through before it's usable to a speaker. The more amplification stages a signal goes through, the more any noise is amplified along with the signal. In the case of a microphone, it's possible that the noise could possibly be just about as strong as the signal itself.
If a signal is very low, any noise that is picked up will be proportiontly more of a problem than that same noise would be with a more powerful signal.
Look at it as if you have a magnetic phono cartridge, which is actually a stronger signal than a microphone but can serve as an example.
It puts out a very small microvolt range signal, travels through a few short wires and then the first thing it sees is a "phono preamp" which, along with some RIAA FR massaging, goes through a major, major gain stage. This brings the signal up to a "line level" signal which can be used by a line stage preamp and even some power amps, if it has enough gain. These "line level" signals can traverse fairly long distances without degradation, particularly when talking home audio.
Most Hi fi units used to have these but as of late, these seem to be disapearing and fall into the realm of aftermarket products.
So, in essense what I'm saying is that while there may be a problem with noise pickup when starting with low, low level signals and going through major gain stages, if the signal is strong enough, and the shielding is strong enough, it can become an audio non issue, except as a source of worry and argument.